MIDTERM LEC: CLEARING Flashcards
Removing dehydrant from tissue, and replacing it with a fluid miscible to both dehydrant and embedding agent
CLEARING
Makes tissues “transluscent” or transparent, hence the term clearing
CLEARING
Most are flammable fluids and have low boiling points
CLEARING
Excessive clearing may cause brittleness
CLEARING
Characteristics of a Clearing Agent:
Miscible with alcohol, paraffin, and mounting media
Causes minimum shrinkage
Should not dissolve Aniline dyes
Should not evaporate quickly in water bath
Makes tissues transparent
CLEARING SOLUTIONS:
- Xylene/Xylol
- Benzene
- Toluene
- Chloroform
- Cedarwood Oil
- Aniline Oil
- Clove Oil
- Carbon tetrachloride
- Tetrachloride
- Methyl benzoate and Methyl salicylate
15-30 mins to 1hr working time (most rapid)
Xylene/Xylol
Most commonly used clearing agent
Xylene/Xylol
Colorless
Xylene/Xylol
Becomes milky when tissues are not completely dehydrated
Xylene/Xylol
Not for nervous tissues and lymph nodes because will cause hardening and shrinkage
Xylene/Xylol
Urgent biopsies and routine purposes (15 to 60 mins); very volatile in paraffin oven
Benzene
Damages the bone marrow leading to aplastic anemia
Benzene
Substitute for xylene or benzene, but slower (1-2hrs)
Toluene
Toxic upon prolonged exposure when used in high conc
Toluene
Does not cause brittleness even when tissues are left for 1 day; not carcinogenic
Toluene
For tissue blocks up to 1cm thick; recommended for large & tough tissues; CNS tissues, lymph nodes, and embryos
Chloroform
Does not make tissues translucent
Chloroform
Toxic to liver, tissues tend to float
Chloroform
For CNS tissues and cytology, smooth muscle, skin
Cedarwood oil
Becomes milky in prolonged storage
Cedarwood oil
Forms crystals with acetic-alcohol fixed tses
(remedy: heat to 200OC prior to using)
Cedarwood oil
For skin and smooth muscle, but tends to be adulterated
Clove Oil
P: for insects, embryos, and delicate tses
Aniline Oil
Properties and disadvantages are similar to
chloroform but is relatively cheaper
Carbon tetrachloride
o For double embedding
o Slow acting
Methyl benzoate and Methyl salicylate
Shortened turnaround time
Tetrahydrofuran
OTHER CLEARING SOLUTION:
- Gum Syrup & Glycerin
- Oil of Bergamot
- Oil of Origanum
- Oil of wintergreen
- Carbon Disulfide
- Carbol Xylene
- Terpineol
- Phenol
- High Test Aviation Lead-free gasoline
for skin and smooth muscle
Oil of Bergamot
used when clearing directly from
water (as in a frozen section)
Gum Syrup & Glycerin
for skin
Oil of Origanum
artificial oil, for delicate tissues
Oil of wintergreen
for smooth muscle; has foul odor
Carbon Disulfide
for friable tissues
Carbol Xylene
for delicate tissues like eyes
Terpineol
for smooth muscles
Phenol
excellent clearing agent
High Test Aviation Lead-free gasoline
